This invention addresses the problem of accidental overturn or rollover of a four wheeled vehicle, such as an automobile or truck. A common cause of such accidents is execution of a steering maneuver involving a sharp turn or swerve, causing the vehicle to tilt. If the lateral force causing the tilt is excessive, the vehicle's body lean can cause the vehicle to roll over, i.e., at least fall onto its side and perhaps continue through further stages of lateral rolling. This type of accident is extreme in its seriousness because the driver has lost all means of controlling the vehicle and has no possible recovery. Accidents of this type can be especially a danger in vehicles with high center of gravity, relative to their wheel track.
The stability of a vehicle is a function of its design, and many experts use the formula T/2H to define a stability ratio, where T=vehicle track and H=vehicle center of gravity height. As is evident from this formula, the stability factor for a vehicle of given track width is highly influenced by height dimension. Trucks tend to be tall relative to wheel track. However, the group of vehicles that presently appears most subject to rollover danger is the sport utility vehicle (SUV), which tends to be a passenger car built on a tall, truck-like chassis, often with four-wheel drive. These vehicles often serve as family cars and are driven by all skill levels of drivers, many of whom lack awareness of this special danger and tend to drive the SUV like an ordinary sedan.
The stability ratio represents the amount of side force, measured in gravity force (g-force) applied at the vehicle's center of gravity, necessary to overturn a rigid body with a given track width and center of gravity height. For example, if a solid car model weighted 3000 pounds and had a track width of 50 inches and a center of gravity height of 24 inches, its stability ratio would be 50/(2.times.24)=1.04. The amount of force needed to overturn the car model can be determined by multiplying vehicle weight by stability ratio. Thus, 3,120 pounds of force applied to the side at the level of the center of gravity will overturn the model on flat ground. Such a result is theoretical only, as it assumes a perfectly rigid vehicle and force applied in only one direction.
Actual cars operating on roads are subject to many other variables, including suspension systems, tire characteristics, and steering inputs. The geometry of a relatively unstable SUV may result in a stability ratio of 1.04, but such a vehicle may roll over on smooth pavement at less than 0.8 lateral g-force. This result is enabled, in part, by flexible tires and suspension systems, which on all vehicles tend to lower the force necessary for rollover below that predicted by T/2H.
The automotive industry has developed measures to improve safety during rollover accidents and in some instances, to assist in preventing them. These measures may employ a computer or processor that anticipates the rollover, based upon data constantly gathered during vehicle operation. For example, the computer may receive information about vehicle attitude, speed, and lateral acceleration, or any other data suited to any specific choice of calculation formula. From gathered data, the processor can predict when rollover danger is high. By automatically adjusting the vehicle suspension system or tire rotation rate, the processor may prevent a rollover that the driver does not anticipate or have skill to correct. Unfortunately, an imminent rollover can be brought about so suddenly, i.e, by an emergency maneuver, that preventative measures of this sort are essentially ineffective. More commonly, the processor improves safety during the rollover by activating safety equipment or seeking to prevent fire. U.S. Pat. No. 5,835,873 to Darby et al., U.S. Pat. No. 5,797,111 to Halasz et al., U.S. Pat. No. 5,610,575 to Gioutsos, U.S. Pat. No. 4,531,607 to Browne, and U.S. Pat. No. 4,377,210 to Monte show prior art of this nature. In each, a computer, sensor, or similar system determines the status of the vehicle. In response to a detected condition, the computer or sensor causes a helpful preparatory action, such as shutting off the fuel pump, tightening a seat belt, spraying lubricant on the windshield, or deploying an air bag.
In areas of automotive technology unrelated to rollover prevention, the automotive industry has developed methods and equipment for improving tire traction under slippery conditions. These methods involve spraying traction increasing materials on the tires or roadway. Examples include U.S. Pat. No. 5,582,411 to Frost, U.S. Pat. No. 5,118,142 to Bish, U.S. Pat. No. 1,959,240 to Josky, U.S. Pat. No. 3,554,370 to Wrede and U.S. Pat. No. 3,256,920 to Byers. These patents show that a vehicle may carry its own supply of sand or other traction-increasing material. Such materials may be sprayed before the vehicle by air pressure in order to assist traction, such as for stopping. A computer may control the application system, operating in response to detected wheel slippage. With the development of antilock braking systems (ABS), the ABS braking computer is well-suited to activate a sand spray unit. This technology potentially can be adapted to preventing rollovers, despite the fact that its application thus far has been directed to the art of stopping and offers little or no assistance to the art of preventing rollovers.
There are a few situations in which a liquid is applied to car tires or brakes for a special purpose, although unrelated to preventing rollovers. U.S. Pat. No. 3,779,324 to Kreske, Jr. shows a manually activated, pressurized, on-board system for spraying detergent onto tires of a drag race car as part of a washing system, to assist the driver in spinning the tires against the road surface just before a drag race to clean the tread. U.S. Pat. No. 4,771,822 to Barbosa teaches spraying tires and brakes in order to cool them. U.S. Pat. No. 3,336,064 to Dzaack teaches spraying tires with a solution of anti-freeze for softening ice to increase tire traction on the ice.
The trend in automotive traction technology as illustrated, above, clearly has been to prevent loss of traction. This approach to designing safety systems seeks to give the driver positive control at all times. Even those systems that oppose rollover do so by attempting to maintain the vehicle in controlled condition. At such time as the physics of rollover dictates that control inevitably will be lost, because the tires leave the ground, the existing systems surrender preventative measures and fall back to accommodating the rollover by activating injury protection devices.
In almost every conceivable situation, it would be desirable to prevent rollover in preference to accepting and accommodating rollover. The potential for extensive property damage, serious injury, and even death in a rollover appears to be so great that extreme prevention measures cannot be ignored. Thus, it would be desirable to prevent rollover by inducing a slide.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method of preventing rollover of this invention may comprise the following.